Merc 850 flywheel punch marks/timing

[buddyp]

On checking the timing on my 75 merc 850 I noticed no timing decal on the shroud..but did notice punch marks on it...from left to right...three in a row top to bottom then about 1 inch to the left another 3 in a row then about 3 inches to the left a single punch mark then about 1 inch to the left another single punch mark...what do these mean?

 

[Gomer50]

Re: Merc 850 flywheel punch marks/timing

I could never really understand what exactly they were for.I have a 72 Merc 80hp and came across a gentleman somewhere on here that explains how to set the timing with the flywheel and the degree's etc.
So here is what I did I measured the flywheel across multiplied that by 3.142 devide that by 360 and you will get how many degree's per inch on the flywheel. 1.5 inches equals 21 degree's BTDC max advance.
6 degree's BTDC equals 0.42 inches. and so on.On your Motor spec's might be a litlle different but the same math.Find TDC and measure and see where the dots line up.I hope this helps.

 

[Chris1956]

Re: Merc 850 flywheel punch marks/timing

The punch marks provide a reference to install the decal, and set the distributor pulley.